Neo4j. Neo4j's Cypher. Samstag, 27. April 13

Transcription

1 Neo4j Neo4j's Cypher 1

2 (Michael)-[:WORKS_ON]-> (Neo4j) console Cypher Community Michael Server Neo4j.org Spring Cloud 2

3 3

4 is a 4

5 NOSQL 5

6 Graph Database 6

7 Some Ways to Learn Cypher 7

8 Focus on this for an hour 8

9 START WHERE Aggregation DELETE BINDS FILTERS RESTRUCTURES REMOVE_FROM Identifier Result BOUND_TO USED_IN BUILDS_UP PAGINATES SKIP/LIMIT Graph FOUND_IN Pattern ADD_TO CREATES DESCRIBES FIX CREATE COMPLETES MATCH RELATE 9

10 The Neo4j Manual docs.neo4j.org 10

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12 The Cypher Reference Card 12

13 Printout at booth 13

14 The Graph Databases Book 14

15 Free Download 15

16 The Neo4j Console 16

17 The Neo4j Console You can share Graphs: 17

18 The interactive Cypher Session 18

19 19

20 A Training Berlin, Frankfurt, Munich, Zurich, Vienna, Hamburg 20

21 Listen carefully during 1st half of this talk 21

22 A project of your own Class-Graph 22

23 Cypher a humane, pattern-matching query language for graphs 23

24 Why Cypher? Not only scale of size is hard Scale of complexity is pretty hard as well 24

25 Cypher attributes #1 Declarative You tell Cypher what you want, not how to get it 25

26 Cypher attributes #2 Expressive Optimize syntax for reading MATCH (a:actor)-[r:acts_in]->(m:movie) RETURN a.name, r.role, m.title 26

27 Cypher attributes #3 Pattern Matching Patterns are easy for your brain 27

28 Cypher attributes #4 Idempotent State change should be expressed idempotently 28

29 Cypher Clauses Some Syntax 29

30 30

31 Cypher: START + RETURN START <lookup> RETURN <expressions> START binds terms using simple look-up directly using known ids or based on indexed Property RETURN expressions specify result set 30

32 Cypher: START + RETURN START <lookup> RETURN <expressions> START binds terms using simple look-up directly using known ids or based on indexed Property RETURN expressions specify result set // lookup node id 0, return that node start n=node(0) return n // lookup node in Index, return that node start n=node:person(name="andreas") return n // lookup all nodes, return all name properties start n=node(*) return n.name 30

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34 Cypher: MATCH START <lookup> MATCH <pattern> RETURN <expr> MATCH describes a pattern of nodes+relationships node terms in optional parenthesis lines with arrows for relationships 31

35 Cypher: MATCH START <lookup> MATCH <pattern> RETURN <expr> MATCH describes a pattern of nodes+relationships node terms in optional parenthesis lines with arrows for relationships // lookup 'n', traverse any relationship to some 'm' start n=node(0) match (n)--(m) return n,m // any outgoing relationship from 'n' to 'm' start n=node(0) match n-->m return n,m // only 'KNOWS' relationships from 'n' to 'm' start n=node(0) match n-[:knows]->m return n,m // from 'n' to 'm' and capture the relationship as 'r' start n=node(0) match n-[r]->m return n,r,m // from 'n' outgoing to 'm', then incoming from 'o' start n=node(0) match n-->m<--o return n,m,o 31

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37 Cypher: WHERE START <lookup> [MATCH <pattern>] WHERE <condition> RETURN <expr> WHERE filters nodes or relationships uses expressions to constrain elements 32

38 Cypher: WHERE START <lookup> [MATCH <pattern>] WHERE <condition> RETURN <expr> WHERE filters nodes or relationships uses expressions to constrain elements // lookup all nodes as 'n', constrained to name 'Andreas' start n=node(*) where n.name='andreas' return n // filter nodes where age is less than 30 start n=node(*) where n.age<30 return n // filter using a regular expression start n=node(*) where n.name =~ /Tob.*/ return n // filter for a property exists start n=node(*) where has(n.name) return n 32

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40 Cypher: CREATE CREATE <node>[,node or relationship] RETURN <expr> create nodes with optional properties create relationship (must have a type) 33

41 Cypher: CREATE CREATE <node>[,node or relationship] RETURN <expr> create nodes with optional properties create relationship (must have a type) // create an anonymous node create n // create node with a property, returning it create n={name:'andreas'} return n // lookup 2 nodes, then create a relationship and return it start n=node(0),m=node(1) create n-[r:knows]-m return r // lookup nodes, then create a relationship with properties start n=node(1),m=node(2) create n-[r:knows {since:2008}]->m 33

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43 Cypher: SET SET [<node property>] [<relationship property>] update a property on a node or relationship must follow a START 34

44 Cypher: SET SET [<node property>] [<relationship property>] update a property on a node or relationship must follow a START // update the name property start n=node(0) set n.name='peter' // update many nodes, using a calculation start n=node(*) set n.size=n.size+1 // match & capture a relationship, update a property start n=node(1) match n-[r]-m set r.times=10 34

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46 Cypher: DELETE DELETE [<node> <relationship> <property>] delete a node, relationship or property must follow a START to delete a node, all relationships must be deleted first 35

47 Cypher: DELETE DELETE [<node> <relationship> <property>] delete a node, relationship or property must follow a START to delete a node, all relationships must be deleted first // delete a node start n=node(5) delete n // remove a node and all relationships start n=node(3) match n-[r]-() delete n, r // remove a property start n=node(3) delete n.age 35

48 Neo4j - the Graph Database 36

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50 (Neo4j) -[:IS_A]-> (Graph Database) Open Source 1 M/s TRA VER SALS Master/Slave HIG H_A VA IL. O ES_T _A S SC AL.net LI CE NS ED _L IK E N _O Clojure JS S E T RA EG T IN PROVIDES NS RU Ruby Index RUN S_A S RU NS Server Lucene ACID TX MySQL Mongo embedded 34bn Nodes Heroku 38

51 Whiteboard --> Data 39

52 Whiteboard --> Data Andreas Peter Allison Emil 39

53 Whiteboard --> Data Andreas knows Peter knows Emil knows knows Allison 39

54 Whiteboard --> Data Andreas knows Peter knows Emil knows knows Allison 39

55 Whiteboard --> Data Andreas knows Peter knows Emil knows knows Allison // Cypher query - friend of a friend start n=node(0) match (n)--()--(foaf) return foaf 39

56 You can use Cypher from all drivers REST:// JDBC 40

57 How to get started? Documentation docs.neo4j.org - tutorials+reference free e-book: Graph Databases Neo4j in Action Spring Data, Good Relationships Get Neo4j Participate a session like this one ;) 41

58 Google "neo4j" [docs.]neo4j.org [news.]neotechnology.com github.com/neo4j neo4j.meetup.com graphconnect.com 42

59 Cypher in Action Software Metrics 43

60 Graphs in Software Technology UML / ER Diagrams are graphs dependencies between classes, packages, modules etc are graphs Software Metrics use dependency analysis Visualizations Cyclomatic Complexity, Fan-in (afferent-coupling) / Fan-out (efferent coupling) etc. 44

61 Code City 45

62 Class Diagram is a Graph 46

63 SonarJ 47

64 But there is more Visualize & Query Method, Field dependencies Collaborative filtering (co-usage) Ranking, God classes Paths between classes Architectural constraints Project dependencies 48

65 Recent project - Software Analytics & Graphs GraphLR - Antlr store - Pavlo Baron NeoMVN - Rickard Öberg Software-Metrics with Neo4j - Raoul Urma Architektur-Constraints - Dirk Mahler Class-Graph - Michael Hunger 49

66 Welcome to Class-Graph take a JAR put it through ASM scan it quickly pull everything into Neo4j add categories, indexes Have Fun 50

67 Welcome to Class-Graph :TYPE ALL_TYPES :ALL_TYPES :ALL_PACKAGES ROOT java.lang. Object :SUPER_TYPE :IN_PACKAGE :SUPER_TYPE :TYPE java.lang. Number :IN_PACKAGE java.lang java.lang. Comparable :lang java :PACKAGE_TREE java.lang. String :SUPER_TYPE :INTERFACE_TYPE :java :PARAM_TYPE java.lang. Integer PKG_TREE valueof :METHOD_OF :FIELD_OF value :RETURN_TYPE :FIELD_TYPE :THROWS int java.lang. NFE 51

68 Task: Find java.lang.number and return it 52

69 Task: Find java.lang.number and return it START o=node:types(name="java.lang.number") RETURN o; 52

70 Task: Subclasses of Number? Return just the name Order them alphabetically 53

71 Task: Subclasses of Number? START n=node:types(name="java.lang.number") MATCH n<-[:super_type]-s RETURN s.name ORDER BY s.name; Return just the name Order them alphabetically 53

72 Task: Which Methods does it have / how many Find the top 5 classes with the most members 54

73 Task: Which Methods does it have / how many START n=node:types(name="java.lang.number") MATCH n-[:method_of FIELD_OF]->m RETURN m; Find the top 5 classes with the most members 54

74 Task: Calculate the fan-out of java.lang.stringbuilder Calculate fan-in Which class has the highest fan-out What about package-level? 55

75 Task: Calculate the fan-out of java.lang.stringbuilder START o=node:types(name="j.l.stringbuilder") MATCH o-[:field_of]->f-[:field_type]->tf, o-[:method_of]->m-[:param_type]->tp, m-[:return_type]->tr RETURN o,count(distinct tf) + count(distinct tp) + count(distinct tr) AS fan_out; Calculate fan-in Which class has the highest fan-out What about package-level? 55

76 Task: Find longest Inheritance Path 56

77 Task: Find longest Inheritance Path START c=node:types(name="java.lang.object") MATCH path=p<-[:super_type*]-c RETURN extract(n in nodes(path) : n.name), length(path) AS len ORDER BY len DESC LIMIT 5; 56

78 Task: Find the class that used IOException most often 57

79 Task: Find the class that used IOException most often START ex=node:types(name="java.io.ioexception" MATCH ex<-[:throws]-m<-[:method_of]-c RETURN c, count(*) ORDER BY count(*) LIMIT 5; 57

80 Task: Which other classes did classes that threw IOException use most often? What could be a source of IOExceptions 58

81 Task: Which other classes did classes that threw IOException use most often? START ex=node:types(name="java.io.ioexception") MATCH ex<-[:throws]-m<-[:method_of]-c, mbr<-[:method_of FIELD_OF]-c, mbr-[:field_type PARAM_TYPE RETURN_TYPE THROWS]->other_type WHERE other_type.name =~ /.+[.].+/ RETURN other_type.name, count(*) ORDER BY count(*) desc LIMIT 10; What could be a source of IOExceptions 58

82 Task: Find a class you like and add a field with your name and some type 59

83 Task: Find a class you like and add a field with your name and some type START c=node:types(name="void"), t=node:types(name="java.lang.reflect.proxy") CREATE c-[:field_of]->(field {name: Michael }) -[:FIELD_TYPE]->t; 59

84 Task: Delete the most annoying class and all its methods, fields and their relationships 60

85 Task: Delete the most annoying class and all its methods, fields and their relationships START c=node:types(name="java.awt.list"), MATCH c-[r1:field_of METHOD_OF]->mbr-[r2]-() c-[r]-() DELETE c,mbr,r1,r2,r; 60

86 Rehash 61

87 START designates the start points 62

88 MATCH describes the pattern 63

89 WHERE filters the result set 64

90 CREATE creates nodes and relationships 65

91 CREATE UNIQUE creates unique patterns 66

92 RETURN projects the results 67

93 WITH chains queries, carries over 68

94 Thanks! Questions? we trade (good) questions for t-shirts 69

95 Visit our booth to chat with us or ask more questions learn more about Neo4j exchange your Q&A-shirt to the right size talk to Philip about the Neo4j Roadmap 70